Radar systems are found for example in both guided and autonomous vehicles, building machinery or manufacturing plants. In particular in a vehicle guided by a driver, radar systems establish values of specific environment parameters, for example a distance from said vehicle to another object, whereby, for example, the decision made by the driver can be supported or said driver can be notified of safety risks. In particular, radar systems for measuring intervals are becoming more frequently used, for example as a parking aid or as collision warning systems in vehicles. Such radar systems which have HF electronics with corresponding HF components, for example HF transmitters and receivers as well as suitable antennae, are operated in particular in the high-frequency range (HF range). Frequently, there are also further radar systems as well as in particular further electronic systems, the functionality of which is impaired by interfering signals emitted by the HF components. In order, additionally, to guarantee a functionality of possible other systems and comply with corresponding EMC standards it is therefore necessary to shield such components in particular from other systems which emit an interfering signal.
For this it is possible to provide a number of circuit boards having HF components with a shielding housing in such a way that said HF components are arranged in a space defined by said shielding housing and the side of the circuit board facing the shielding housing, also called circuit board upper face. In particular, this helps define a shielding region on said circuit board. Said shielding housing is typically made from an electrically conductive material. Additionally, on the side of said circuit board facing away from the shielding housing, also called circuit board lower face, there is frequently formed a shielding in such a way that said HF components are surrounded, substantially completely, by an electrically conductive material.
However, in the case, for example, of a radar system, it is necessary to provide an HF signal as a useful signal for an antenna outside of said shielding region. However, an additional opening in said shielding housing drastically degrades its shielding properties. To prevent such a degradation, said useful signal can be routed beneath said shielding housing by means of a so-called strip transmission line. The disadvantage here is that, in order to design said strip transmission line, a conductor must be developed inside the circuit board substrate, as a result of which in actual fact a multilayer system is present, i.e. two substrate layers arranged one on top of the other are required, with a line arranged between these layers. Additionally, microstrips are frequently used within said shielding housing which are simpler to produce and are more space-saving than strip transmission lines, as a result of this a junction from microstrip to strip transmission line is required. However, such a junction creates disadvantageous reflection losses, i.e. a reduction of said signal.
Alternatively, said useful signal can also be guided from the uppermost layer which has said HF components via throughplatings onto a second substrate layer arranged beneath said circuit board upper face and routed beneath said shielding housing by means of a microstrip. In other words, said useful signal can be routed beneath said shielding housing by means of a microstrip developed on a lower substrate layer. However, a junction between the different substrate layers is needed to do this. Also, such a junction is disadvantageously lossy. Furthermore, it is disadvantageous that both alternatives are correspondingly costly due to the multilayer system required. Because an HF substrate which is typically more costly in comparison with conventional circuit board substrates is used to develop layers which conduct HF signals, both alternatives are also correspondingly cost-intensive.